Management and long-term haematological and neurological outcomes of Immunoglobulin M and Waldenström's macroglobulinaemia-related neuropathy: A single-centre experience.

Immunoglobulin M-related peripheral neuropathy (IgM-PN) is typically demyelinating and associated with anti-myelin-associated glycoprotein antibodies; however, limited data on clinical outcomes are available. We retrospectively analysed consecutive patients with IgM-PN assessed prospectively with the Rasch-built Overall Disability Scale (RODS) and the Inflammatory Neuropathy Cause and Treatment (INCAT) questionnaires. Twenty-eight patients were retrospectively enrolled. The median follow-up was 5.54 years. Treatment was initiated in all solely due to neuropathy symptoms: 19 (67.9%) dexamethasone-rituximab-cyclophosphamide, 6 (21.4%) rituximab and 3 (10.7%) ibrutinib. The baseline median INCAT score was 2.0 and improved to 1.0 at further time points; within-patient improvements compared to baseline were significant (p < 0.005). A clinically relevant improvement was evident in 13 (46.4%), 18 (64.3%) and 17 (60.7%) patients at 6, 12 and 24 months respectively. IgM reduction was associated with improvement in INCAT scores at 6 (p = 0.041) and 12 months (p = 0.030). At baseline, the median RODS score was 38.0, improved to 41.5 at 6 months, then to 43.0 and 43.5 at 1 and 2 years (all p < 0.001). A clinically relevant improvement was evident in 5 (17.9%), 7 (25%) and 9 (32.1%) patients at 6, 12 and 24 months respectively. Patients with IgM-PN, treated mainly with rituximab-based regimens, showed significant improvement in functional and neurological ability over a 2-year follow-up.